1. Field of the Invention
The present invention relates to a support of a displacement-detection device such as a magnetic encoder with magnetoresistive effect (MR) elements, to a sensor support assembly, and to the displacement-detection device. Particularly, the present invention relates to a support of a displacement-detection device such as a rotary encoder used for detecting a displacement of a rotary lens barrel of a camera, to a sensor support assembly, and to the displacement-detection device.
2. Description of the Related Art
Demand for high resolution and downsizing in a magnetic rotary encoder is now proceeding because of the need for more precise control of the rotation angle. The higher resolution and more downsizing in the magnetic rotary encoder, the larger influence of a gap between a magnetic medium and a magnetic sensor of the encoder occurs. Therefore, in order to provide high resolution and downsizing, it is requested to keep the gap at constant.
Because a sliding structure for sliding the magnetic sensor on the surface of the magnetic medium with keeping the sensor in contact with the magnetic medium is effective to proceeds the high resolution and downsizing, many of the recent magnetic encoders adopt such sliding structure. However, when a magnetic rotary encoder with the sliding structure has a typical flat-shaped magnetic sensor, it is quite difficult to precisely mount this flat-shaped magnetic sensor on the encoder. Thus, such magnetic sensor may sometimes incline in a direction perpendicular to the magnetized pitch of the magnetic medium, that is, the magnetic sensor may sometimes pitch with respect to the magnetic medium. In this case, a gap at the sensing portion may vary causing fluctuations or reductions in sensor output even when the magnetic sensor partly contacts to the magnetic medium.
Japanese patent publication No.2000-205808A discloses a sliding type magnetic rotary encoder with a pressure spring for applying pressure to a magnetic sensor that can be swung around the swing center axis nearly parallel to a displacement direction of a magnetic medium in order to prevent the magnetic sensor from slanting to the magnetic medium.
Japanese patent publication No.2003-240603A discloses a pressure spring for supporting a magnetic sensor. The spring has folded arms for pressing the magnetic sensor with uniform force to prevent the magnetic sensor from slanting to a magnetic medium.
Japanese patent publication No.62-051020A discloses a suspension of a head support mechanism for magnetic disk drive but not for a magnetic rotary encoder. The suspension has a two-spring structure of a lifting spring and a folded spring to sufficiently respond to the movement in a direction perpendicular to the disk surface and also to have enough stiffness in a direction parallel to the disk surface, so that a magnetic head follows up-down movement of the disk surface without tilting.
However, since the configuration disclosed in Japanese patent publication No.2000-205808A requires a load point capable of swinging, structure of this load point becomes complicated. Also, because the pressure spring is long, it is very difficult to miniaturize the configuration. Furthermore, because the structure disclosed in this publication is made to forcefully adjust the inclination of the head with respect to the magnetic medium by applying the pressure, it is required to provide considerably high pressure.
Since the pressure spring disclosed in Japanese patent publication No.2003-240603A is folded, it is possible to somewhat downsize the spring. However, because the spring is folded only one time, enough downsizing of the pressure spring cannot be expected. Also, because of the one-time folded structure of the spring, it is difficult to move up-and-down the magnetic sensor without changing its attitude. Therefore, when the position of the magnetic medium varies or variations in the attached position of the magnetic sensor occurs, a pitch angle of the magnetic sensor varies causing change in the gap between the sensing portion of the magnetic sensor and the magnetic medium to increase to an extent that cannot neglect. Particularly, if the total length of the pressure spring is shortened, the gap change in response to the variation in the pitch angle of the magnetic sensor more increases.
Since the suspension disclosed in Japanese patent publication No. 62-051020A is designed specifically for the magnetic disk drive and has the two-spring structure with the lifting spring and the folded spring, its structure itself is complicated. Also, because the folded spring used has one-time folded structure, it is quite difficult to move up-and-down the magnetic head without changing its attitude.
Furthermore, in the conventional high-resolution downsized magnetic encoder, a stress from a wiring member may be applied to a magnetic sensor inducing difficulty in the attitude control of the magnetic sensor when the suspension deforms in response to the up-and-down movement of the sensor. Particularly, when the length of the wiring member is short, the up-and-down movement of the sensor wields a very large influence over the attitude control of the magnetic sensor.